Fix source maps caching key

lib/sprockets/source_map_processor.rb

@@ -21,6 +21,12 @@ def self.call(input)
       asset  = env.load(uri)
       map    = asset.metadata[:map] || []
 
+      # TODO: Because of the default piplene hack we have to apply dependencies
+      #       from compiled asset to the source map, otherwise the source map cache
+      #       will never detect the changes from directives
+      dependencies = Set.new(input[:metadata][:dependencies])
+      dependencies.merge(asset.metadata[:dependencies])
+
       map.map { |m| m[:source] }.uniq.compact.each do |source|
         # TODO: Resolve should expect fingerprints
         fingerprint = source[/-([0-9a-f]{7,128})\.[^.]+\z/, 1]
@@ -35,7 +41,7 @@ def self.call(input)
 
       json = env.encode_json_source_map(map, filename: asset.logical_path)
 
-      { data: json, links: links }
+      { data: json, links: links, dependencies: dependencies }
     end
   end
 end

test/fixtures/source-maps/dynamic/application.coffee

@@ -0,0 +1,4 @@
+#= require dynamic/unstable
+
+document.on 'dom:loaded', ->
+  console.log("Hi")

test/test_source_maps.rb

@@ -51,6 +51,27 @@ def setup
     ], map.map { |m| m[:source] }.uniq.compact
   end
 
+  test "rebuilds a source map when related dependency has changed" do
+    filename = fixture_path('source-maps/dynamic/unstable.js')
+    sandbox filename do
+      write(filename, "magic_number = 42", 1421000000)
+      map_1 = JSON.parse(@env['dynamic/application.js.map'].source)
+
+      write(filename, "number_of_the_beast = 666", 1422000000)
+      map_2 = JSON.parse(@env['dynamic/application.js.map'].source)
+
+      assert_equal([
+        "dynamic/unstable.source-43b85c2116b8c894a292c17a6845aa1c9b1491f7dc6bddf764c384668457d55a.js",
+        "dynamic/application.source-5cc94f82fada13ee8ef969d4cef2018e52ce42f9e1c8ccb6f8333cdc0dd5d3b5.coffee"
+      ], map_1["sources"])
+
+      assert_equal([
+        "dynamic/unstable.source-2ae6f42425799bc9f718842df81be58c5f011dc93a00ca4da17be8877bdb02b3.js",
+        "dynamic/application.source-5cc94f82fada13ee8ef969d4cef2018e52ce42f9e1c8ccb6f8333cdc0dd5d3b5.coffee"
+      ], map_2["sources"])
+    end
+  end
+
   test "compile coffeescript source map" do
     assert asset = @env.find_asset("coffee/main.js")
     assert_equal fixture_path('source-maps/coffee/main.coffee'), asset.filename